Direct Current Supply Research Articles

A Grid-Forming Converter with MVDC Supply and Integrated Step-Down Transformer: Modeling, Control Perspectives, and Control Hardware-in-the-Loop (C-HIL) Verification

A grid-forming voltage source converter with an integrated step-down transformer could be a promising solution for supplying low-voltage alternating current loads from a medium-voltage direct current supply. However, it may require a control system that gathers feedback signals from both the primary and secondary sides of the transformer, which in turn complicates the derivation of a standard form linear model. The absence of such a model complicates control tuning, as well as the assessment of dynamics and stability of the converter system. The objective of this paper is to address this gap in knowledge. For the case study, a conventional H-bridge converter with a step-down transformer and an αβ-frame dual-loop grid-forming controller is considered. Initially, comprehensive guidelines on deriving a standard form linear model for this converter system are presented. Then, the impact of controlling the VSC in a dq frame and the changes in the transformer vector group on the small-signal model of the VSC are analyzed. The aspects of control tuning are also discussed in detail, and the model’s accuracy and efficacy are validated both theoretically and through control hardware-in-the-loop (C-HIL) tests using a Typhoon HIL setup.

The experimental and DFT approaches on electronic, thermal and conductivity properties of non-linear optical bearing fused aromatic chalcones towards prospective OLEDs

New derivatives of push-pull chalcone was successfully synthesized to demonstrate as NLO active on the impact of organic light emitting diode (OLED) materials. A total of three fused-aromatic chalcones (AA, AB, AC) with different substituents have been characterized through TGA, Z-scan analysis, 1H & 13C NMR, IR and UV–Vis. All the targeted compounds are nonlinear refraction (NLR) active with the range of χ(3) (∼ × 10–6 esu). AC reveals the highest value of first order hyperpolarizability (βtot) at 528.08 × 10–30 esu upon the substitution of strong electron acceptor. Theoretical investigation was performed by employing the theory of B3LYP/6–31 G (d,p) level via density functional theory (DFT) to optimize the geometries, molecular electrostatic potential (MEP) and frontier molecular orbitals (FMO). The predicted electronic properties of the molecule are supported by the experimental results, confirming the theoretical conclusions. The examination of its potential as emissive layer in OLED application was constructed on ITO substrate for electroluminescence behaviour evaluation under various direct current (DC) voltages supply. The preliminary outcomes reveal that these simple chalcone derivatives are capable of being utilised in any optoelectronic application.

Electric current stressing enhanced damping properties in Sn5Sb solder

PurposeThe purpose of this paper is to investigate the effects of electric current stressing on damping properties of Sn5Sb solder.Design/methodology/approachUniformly shaped Sn5Sb solders were prepared as samples. The length, width and thickness of the samples were 60.0, 5.0 and 0.5 mm, respectively. The damping properties of the samples were tested by dynamic mechanical analyzer with a cooling system to control the test temperature in the range of −100 to 100°C. Simultaneously, electric current was imposed to the tested samples using a direct current supply. After tests, the samples were characterized using scanning electron microscope, electron backscatter diffraction and transmission electron microscope, which was aimed to figure out the damping mechanism in terms of electric current stressing induced microstructure evolution.FindingsIt is confirmed experimentally that the increase in damping properties is due to Joule heating and athermal effects of current stressing, in which Joule heating should make a higher contribution. G–L theory can be used to explain the damping properties of strain amplitude under current stressing by quantitative description of geometrically necessary dislocation density. While the critical strain amplitude and high temperature activation energy decrease with increasing electric current.Originality/valueThese results provide a new method for vibration reliability evaluation of high-temperature lead-free solders in serving electronics. Notably, this method should be also inspiring for the mechanical performance evaluation and reliability assessment of conductive materials and structures serving under electric current stressing.

A Voltage-Level Optimization Method for DC Remote Power Supply of 5G Base Station Based on Converter Behavior

Unlike the concentrated load in urban area base stations, the strong dispersion of loads in suburban or highway base stations poses significant challenges to traditional power supply methods in terms of efficiency and cost. High-voltage direct current (HVDC) remote supply have better application potential in this scenario due to their low transmission losses, attracting much attention. However, existing research has problems such as ambiguous optimal power supply distance under different voltage levels and a lack of behavioral models for converters. Therefore, this paper starts from the behavior of underlying converters, analyzes the loss composition of different converters in HVDC long-distance supply, and establishes a refined model for converters by determining the mathematical relationship between converter losses and operating power. Considering the economic feasibility of power supply solutions throughout the lifecycle, a modeling method is proposed that optimizes the voltage level of converters considering the behavior of converters for different supply distances. The optimal voltage level for different supply distances is discussed, and the effectiveness of the model is verified through examples, providing valuable guidance for optimizing the voltage level in HVDC long-distance supply for 5G base stations.

Design and construction of a DC – DC power supply for powering USB soldering iron

Power supply is an electrical device that converts electric current from a source to the desired voltage, current and frequency to power an electrical load. The universal serial bus (USB) soldering iron available in the market operates on a 5-volt direct current (DC) supply. Essentially, it can be powered by any cell phone charger that is capable of providing an output power of not less than 8 watts. Absence of constant power supply from the national grid at times inhibit effective use of this soldering iron. To power it directly from storage battery is inappropriate as most batteries are rated as 2.7, 3.7, 6, and 12 volts. This paper deals with the design and construction of an inexpensive portable regulated power supply to power a USB soldering iron from a 12 volt power supply. The circuit was designed and simulated using Proteus software “intelligent schematic input system (ISIS)” before the construction procedure. Deep discharge protection that safeguard storage battery against under voltage and reverse polarity protections were added to the design. These special features distinguished it from those available in the market. Two light emitting diodes (LED) serve as indicators for low and normal condition of battery while sound from a buzzer shows that the input terminals of the circuit were wrongly connected. The system was tested and found to work as anticipated.

An electrogenetic interface to program mammalian gene expression by direct current

Wearable electronic devices are playing a rapidly expanding role in the acquisition of individuals’ health data for personalized medical interventions; however, wearables cannot yet directly program gene-based therapies because of the lack of a direct electrogenetic interface. Here we provide the missing link by developing an electrogenetic interface that we call direct current (DC)-actuated regulation technology (DART), which enables electrode-mediated, time- and voltage-dependent transgene expression in human cells using DC from batteries. DART utilizes a DC supply to generate non-toxic levels of reactive oxygen species that act via a biosensor to reversibly fine-tune synthetic promoters. In a proof-of-concept study in a type 1 diabetic male mouse model, a once-daily transdermal stimulation of subcutaneously implanted microencapsulated engineered human cells by energized acupuncture needles (4.5 V DC for 10 s) stimulated insulin release and restored normoglycemia. We believe this technology will enable wearable electronic devices to directly program metabolic interventions.

Novel excitation structure to improve the performance of a miniature radio frequency ion thruster

This letter reports a new magnetic field-enhanced radio frequency (RF) ion thruster, which uses a high-frequency shielding network to isolate the direct current and RF supplies. This provides an additional magnetic field for a novel magnetized RF ion thruster (HRIT-4M) without changing the original thruster structure. The results show an improvement in the performance of an RF ion thruster in a verified magnetic field. Compared to other excitation structures, this excitation structure is simpler and more efficient. However, it is influenced by factors such as the size of the discharge chamber and pressure, which should be further investigated.

Spin-wave dynamics controlled by tunable ac magnonic crystal

The magnonic crystal, which has a spatial modulation wave vector $q$, couples the spin wave with wave vector $k$ to the one with wave vector $k\ensuremath{-}q$. For a conventional magnonic crystal with direct current (dc) supply, the spin waves around $q/2$ are resonantly coupled to the waves near $\ensuremath{-}q/2$, and a band gap is opened at $k=\ifmmode\pm\else\textpm\fi{}q/2$. If instead of the dc current the magnonic crystal is supplied with an alternating current (ac), then the band gap is shifted to $k$ satisfying $|{\ensuremath{\omega}}_{s}(k)\ensuremath{-}{\ensuremath{\omega}}_{s}(k\ensuremath{-}q)|={\ensuremath{\omega}}_{\mathrm{ac}}$; here ${\ensuremath{\omega}}_{s}(k)$ is the dispersion of the spin wave, while ${\ensuremath{\omega}}_{\mathrm{ac}}$ is the frequency of the ac modulation. The resulting gap in the case of the ac magnonic crystal is the half of the one caused by the dc with the same amplitude of modulation. The time evolution of the resonantly coupled spin waves controlled by properly suited ac pulses can be well interpreted as the motion on a Bloch sphere. The tunability of the ac magnonic crystal broadens the perspective of spin-wave computing.

Minireview on Cathodic and Anodic Exfoliation for Recycling Spent Zinc–Carbon Batteries To Prepare Graphene Material: Advances and Outlook of Interesting Strategies

The recycling of spent batteries has always been a daunting and difficult task throughout the long history of battery development. Zinc–carbon batteries, one of history’s most popular batteries, still widely used today, have become a serious environmental problem. Although zinc–carbon batteries are the first primary batteries that belong to non-rechargeable cells, they are still widely used as a result of their low cost and ease of product. Currently, thousands of tons of zinc–carbon batteries are released into the environment each year, requiring advanced recycling methods. Among various strategies that have been developed, electrochemistry is one of the interesting methods, with the advantages of being cheap and fast and able to synthesize a new material, graphene, a material that changes the technology game. Graphene derived from carbon rods in spent zinc–carbon batteries has been successfully synthesized by a short-time, simple instrumentation of electrochemical exfoliation under direct current supply, which demonstrates a low-cost and environmental strategy for mass production of graphene material from electronic device waste. This review provides a great overview aiming to introduce the electrochemical exfoliation method to recycle spent zinc–carbon batteries to synthesize graphene materials, which contributes to battery recycling technology as an alternative strategy.

Scientific Assessment of Locally and Factory Built 2 KVA Modified Sine Wave Solar Powered Inverters

This paper presents scientific assessment of locally and factory built 2 kvA modified sine wave inverters. A data logger known as DENT ELITE PRO SP which was connected across the two solar inverters to collect relevant data. The captured data were harmonic distortion, voltage and current variation in the outputs of the solar inverters. An integrated circuit (IC) SG3524 was used to generate the necessary pulse needed to drive the MOSFET (3205IRF) to alternate the direct current (DC) supply. The output from the oscillator stage was amplified using power transistor MOSFET. The frequency at which circuit operate is determined with the oscillator stage. There were different points of interception for both current and voltage for both types of inverters over a stipulated period. The assessment summarily showed that the measurements for the factory made inverter range from 226.044V to 230.811V and these values were within the nominal voltage. However, for locally made inverter, the voltage measurements for the period under consideration were within 215.189V and 221.599V and this depicts a slight deviation from the nominal voltage values. The result showed that the factory built inverter is superior to the locally fabricated type and this implies that there should be improvement in the design of oscillating stage and the determination of the drain current of theMOSFET should be accurate.

Portable Iontophoresis Device for Efficient Drug Delivery.

The timely delivery of drugs to specific locations in the body is imperative to ensure the efficacy of treatment. This study introduces a portable facial device that can deliver drugs efficiently using iontophoresis. Two types of power supplies-direct current and pulse ionization supplies-were manufactured by injection molding. Electrical stimulation elements, which contained Ag metal wires, were woven into facial mask packs. The diffusion phenomenon in the skin and iontophoresis were numerically modeled. Injection molding was simulated before the device was manufactured. Analysis using rhodamine B demonstrated a remarkable increase in the moisture content of the skin and effective absorption of the drug under an applied electric field upon the application of iontophoresis. The proposed concept and design constitute a new method of achieving effective drug absorption with wearable devices.

Nitriding of Long-Term Holes in the Cyclic-Commuted Discharge

The effect of anhydrous nitriding in a glow discharge on microhardness, phase composition, and wear resistance of long holes in steels C45, 37Cr4, and 41CrAlMo7 with direct current supply and in cyclically switched discharge (CSD) was studied. Nitriding was carried out on a UATR-1 anhydrous nitriding unit with a discharge chamber diameter of 400 mm and a working height of 700 mm. Anhydrous nitriding in a glowing discharge was carried out at a temperature of 560 °С, a voltage of 730 V, a pressure in the chamber of 120 MPa, and the nitriding duration was 6 h. It was established that using holes with a relatively small diameter of glow discharge in a cyclically switched discharge for nitriding creates conditions for obtaining modified layers with higher physical, mechanical, and tribological characteristics. The results of microhardness measurement and their comparison with X-ray phase analysis data confirm the formation of ε, γ, and α phases during nitriding along the entire height of the samples placed in the experimental model. The tests carried out in the dry friction mode showed an increase in the wear resistance of samples made of steel C45, 37Cr4, and 41CrAlMo7 during nitriding in a cyclically switched discharge. To achieve 100 μm wear of 41CrAlMo7 steel during nitriding in CSD, 1400 m of friction path and 1000 m – during nitriding with direct current is required. It was established that using long holes of a glow discharge with different types of power for nitriding creates conditions for obtaining modified layers with variable characteristics. Nitriding of holes with a relatively small diameter of a glow discharge with a different power supply creates conditions for obtaining modified layers with different physicomechanical and tribological characteristics.

Low Voltage Direct Current Supply and Utilization System: Definition, Key Technologies and Development

Low Voltage Direct Current Supply and Utilization System: Definition, Key Technologies and Development

Flow control performance evaluation of a tri-electrode sliding discharge plasma actuator

Tri-electrode sliding discharge (TED) plasma actuators are formed by adding a direct current (DC) exposed electrode to conventional dielectric barrier discharge (DBD) plasma actuators. There are three TED modes depending on the polarity and amplitude of the DC supply: DBD discharge, extended discharge and sliding discharge. This paper evaluates the electrical, aerodynamic and mechanical characteristics of a TED plasma actuator based on energy analysis, particle image velocimetry experiments and calculations using the Navier–Stokes equation. The flow control performances of different discharge modes are quantitatively analyzed based on characteristic parameters. The results show that flow control performance in both extended discharge and sliding discharge is more significant than that of DBD, mainly because of the significantly higher (up to 141%) body force of TED compared with DBD. However, conductivity loss is the primary power loss caused by the DC polarity for TED discharge. Therefore, power consumption can be reduced by optimizing the dielectric material and thickness, thus improving the flow control performance of plasma actuators.

Experimental analysis of electro-jet machining of thin metal sheets under the application of ultrasonic vibration, continuous and pulsed direct current

Electrochemical machining is considered to be suitable for precision and micromachining without the development of residual stress, mechanical distortion and thermal damage. In this work, an in-house developed electro-jet machining system, a variant of electrochemical machining, has been used for machining in thin metal sheets, where the electrolyte is supplied in the form of a fine jet, concentrically to a wire electrode, through a nozzle. Machining performance was studied for generation of through slits of sub-millimetre range in 500 μm thick aluminium sheets, under the application of continuous and pulsed direct current (DC) power sources as well as with the application of ultrasonic vibration to the workpiece, emphasizing achieving better dimensional control with minimum overcut. A detailed investigation of the effect of applied voltage, scan speed, inter-electrode gap and electrolyte concentration has been performed in the case of continuous DC supply on quality factors, kerf-width, amount of overcut and material removal rate. Furthermore, the effects of duty cycle and pulse frequency in the case of pulsed DC supply, and the effect of vibration frequency under the application of ultrasonic vibration have been analysed on the above-mentioned output factors. Though a pulsed DC power supply with a pulse frequency of more than 1 kHz and a small duty cycle was found suitable for precision machining among all conditions, ultrasonic vibrations proved beneficial for fine feature generation with tighter size control at higher frequencies (lower vibration amplitude).

Evaluation of Operating Range of a Machine Emulator for a Back-to-Back Power-Hardware-in-the-Loop Test Bench

Inverter testing using laboratory test benches with rotating machines can be bulky, complex, and maintenance intensive. One solution is to use machine emulator for laboratory testing of inverters. The emulator is controlled in such a way that currents and voltages at the terminals resemble a machine connected to a mechanical load. A machine emulator for a back-to-back power-hardware-in-the-loop (PHIL) test bench is proposed in this article. The PHIL test bench consists of two identical voltage source converters (VSCs) with three single-phase inductors as coupling network. The two VSCs are connected to the same direct current supply. One VSC acts as inverter under test (IUT), while the other is part of machine emulator. Aim of this article is to analyze the influence of coupling inductance on operating range of the emulator. An analytical method to dimension the coupling inductance is introduced and verified in experiments. The operating range of the emulator is also evaluated. The performance of the IUT when tested with an equivalent permanent magnet synchronous motor in simulations and that of a prototyped 60-kW rated machine emulator are compared. Sensitivity of emulator control on parameter estimation is discussed. The experimental results show good agreement with simulations in both steady-state and dynamic conditions.

ICARUS-Q: Integrated control and readout unit for scalable quantum processors.

We present a control and measurement setup for superconducting qubits based on the Xilinx 16-channel radio-frequency system-on-chip (RFSoC) device. The proposed setup consists of four parts: multiple RFSoC boards, a setup to synchronize every digital to analog converter (DAC) and analog to digital converter (ADC) channel across multiple boards, a low-noise direct current supply for tuning the qubit frequency, and cloud access for remotely performing experiments. We also designed the setup to be free of physical mixers. The RFSoC boards directly generate microwave pulses using sixteen DAC channels up to the third Nyquist zone, which are directly sampled by its eight ADC channels between the fifth and the ninth zones.

Use of DSLR and Sonic Cameras to Detect and Locate High-Voltage Corona Discharges.

Corona discharges are a concern in high-voltage applications. It is of utmost importance to detect and locate the discharges at an early stage using simple methods for this purpose. This paper evaluates and compares the sensitivity of two methods for detecting and locating the source of discharges, which are based on a digital single-lens reflex (DSLR) camera and a portable wideband sonic camera incorporating a matrix of micro-electromechanical systems (MEMS) microphones. Both cameras can generate an image of the studied area where the discharge sites are identified. The study is carried out with different electrode geometries, 50 Hz alternating current (ac) and positive and negative direct current (dc) supplies, and the effect of the distance between the sensor and the discharge sites is also analyzed. The presented results show that the sonic camera enables fast, simple, and sensitive detection and localization of the source of corona discharges even at a very early stage in daylight conditions, regardless of the type of power supply, that is, ac or positive/negative dc, and at distance of several meters from the discharge source.

Analysis of electric current supply circuits to rolls during electroplastic rolling of tungsten microstrips

One of the important problems in the design and operation of the electroplastic deformation mill is the reliability and uniformity of the supply of powerful electric current to the deformation zone. The high density of the electric current and the uneven distribution of it leads to a different manifestation of the effect of electroplasticity along the width of the strip, an uneven temperature field, and as a result, to a decrease in the quality of the finished product. To evaluate various current supply circuits, a discrete model is proposed, in which the work rolls and the rolled strip are presented as combinations of lumped resistances. The model was used when considering four main circuits for supplying electric current to the rolls of the electroplastic deformation strip mill: straight one-sided, diagonal onesided, direct two-sided, diagonal two-sided. For all circuits, formulas were obtained for calculating the electric currents flowing in the center of the strip and along its edges. The dependences obtained using the developed model show that the greatest non-uniform distribution of electric current across the width of the rolled strip occurs with a direct one-sided current supply. At the same time, its undoubted advantage over other options is a simpler design. Diagonal single-sided and both variants of double-sided current supply (according to this model) give the same results. The main disadvantage of these options is the need to supply electric current from both sides of the rolling mill. Regardless of the selected current supply option, it is necessary to minimize the ratio of the electrical resistances of the roll materials and the deformed material. In particular, this can be achieved by increasing the diameter of the work roll, as well as by choosing a roll material with high electrical conductivity. The model for supplying electric current to the work rolls and recommendations for reducing the uneven distribution of current across the width of the strip are used in the design of electroplastic deformation mills.

Microwave-ignited DC-plasma ejection from basalt: Powder-generation and lightning-like effects

A phenomenon of dusty plasma ejected from basalt is presented, in the form of a stable, long-lived fire-pillar, solely sustained by a direct-current (DC) supply. The plasma is emitted to the air atmosphere from a molten hotspot, initially created in the basalt rock by localized microwave-heating (LMH). After an LMH-to-DC transition, the plasma column is solely sustained as a fire-pillar of ∼2 cm diameter, ∼4-cm height using a DC supply of ∼0.2 kV, ∼5 A, steadily lasting for periods longer than 3 min. The dusty-plasma products, accumulated in a powder form, consist of micro- and nanoparticles of basalt's components, including oxides of Si, Na, Fe, P, K, Mg, and Ti. The experimental conditions for the DC sustainability of basalt's dusty-plasma column are analyzed by various theoretical estimates. A possible relevance of these laboratory observations is attributed to atmospheric fire-pillar-like effects, associated, for instance, with volcanic-, ball-lighting, and lunar dusty-plasma phenomena. A potential application, utilizing this effect of DC-sustained dusty-plasma columns, is proposed for the direct extraction of mineral powders from rocks.